/*
  一、将下面异步代码使用Promise的方式改进
    setTimeout(function() {
      var a = 'hello'
      setTimeout(function() {
        var b = 'lagou'
        setTimeout(function() {
          var c = 'I ❤ U'
          console.log(a + b +c)
        }, 10)
      }, 10)
    }, 10)
 */

const getTimer = (str) => {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve(str)
    }, 10)
  })
}

new Promise((resolve, reject) => {
  resolve()
}).then(() => {
  return getTimer('hello')
}).then(value => {
  return getTimer(value + ' ' + 'lagou')
}).then(value => {
  return getTimer(value + ' ' + 'I ❤ U')
}).then(console.log)